1. Field
One embodiment of the invention relates to a technique associated with a printed wiring board.
2. Description of the Related Art
Many printed wiring boards are each constituted of a plurality of members different from each other in thermal expansion coefficient. As a result, in a printed wiring board, internal stress occurs at the time of reflow, and a warp is caused in some cases.
In Japan Pat. Application KOKAI Publication No. 2006-278747, a flexible printed wiring board with a reinforcing plate in which a warp due to heat is restrained from occurring by the reinforcing plate is disclosed. The reinforcing plate comprises cylindrical holes uniformly arranged at predetermined intervals in such a manner that glass fibers in the reinforcing plate are cut into lengths of 15 mm or less.
Incidentally, it is desired that a warp be restrained from occurring in the printed wiring board.